This application incorporates by reference the entire disclosure of U.S. patent application Ser. No. 09/747,173, entitled xe2x80x9cSUSCEPTOR POCKET PROFILE TO IMPROVE PROCESS PERFORMANCE,xe2x80x9d filed Dec. 22, 2000.
The present invention relates generally to substrate holders and, in particular, to substrate holders configured to prevent heat loss at the outer peripheral edge of the holder.
High-temperature ovens, or reactors, are used to process substrates for a variety of reasons. In the electronics industry, substrates such as semiconductor wafers are processed to form integrated circuits. A substrate, typically a circular silicon wafer, is placed on a substrate holder. If the substrate holder helps to attract radiant heat, it is called a susceptor. The substrate and substrate holder are enclosed in a reaction chamber, typically made of quartz, and heated to high temperatures by a plurality of radiant heat lamps placed around the quartz chamber. In an exemplary high temperature process, a reactant gas is passed over the heated substrate, causing the chemical vapor deposition (CVD) of a thin layer of the reactant material onto a surface of the substrate. Through subsequent processes, these layers are made into integrated circuits.
It is generally desirable to maintain a uniform temperature throughout the substrate holder during substrate processing. Typically, the substrate temperature closely tracks that of the substrate holder. Non-uniformities in the temperature of the substrate holder result in non-uniformities in the substrate temperature. These temperature gradients can leave the substrate susceptible to crystallographic slip in the single-crystal substrate and epitaxial layers, and possible device failure. Thus, temperature uniformity is desirable to minimize these problems. Another reason why it is desirable to maintain a uniform temperature throughout the substrate holder is to prevent differences in the quality of the film deposited on the substrate. Generally, temperature gradients in the substrate result in different rates of deposition, and thus non-uniformities, throughout the substrate.
Using state of the art apparatuses and methods, temperature uniformity has been achieved throughout most of the combination of the substrate and the substrate holder. However, it is difficult to keep the radially outer region of the substrate/holder combination (the xe2x80x9ccombinationxe2x80x9d) as hot as the inner region. This is because the radially outer region experiences greater convective and conductive heat loss and, in many existing apparatuses, receives less direct radiation.
The radially outer region of the substrate/holder combination experiences greater convective heat loss than the remainder of the combination because the outer region has a generally vertical side edge and, hence, a larger surface area at which heat loss occurs. The outer region of the combination can also lose conductive heat due to contact with other equipment. These disparities in heat loss between the radially outer region and the remainder of the combination result in a lower temperature in the outer region. In some reactors, this temperature disparity is heightened because the vertical side edge of the combination receives less direct radiation from the heat sources. This temperature disparity produces a different deposition rate and deposited film thickness near the outer edge of the substrate. Accordingly, a processed substrate is typically characterized by an xe2x80x9cexclusion zonexe2x80x9d near the substrate edge, within which the deposited film has non-uniform qualities.
Some prior art attempts to minimize or remove the exclusion zone have focused upon directing a greater amount of radiant energy to the radially outer, as opposed to inner, region of the substrate holder during processing, in order to lessen the disparity in heat loss between such regions. Other attempts have focused upon providing a hot annular structure (e.g., a temperature compensation ring) near the periphery of the substrate holder, to reduce the heat loss from the outer region. While these efforts have been helpful, some disparity in heat loss between the inner and outer regions remains. Using state of the art processing methods and apparatuses, the annular thickness of exclusion zones is generally about 10-20 mm, while chip manufacturers strive to enforce exclusion zones as small as 3 mm to maximize yield. A need exists to further shrink the exclusion zone.
Accordingly, it is a principle object and advantage of the present invention to overcome these limitations and to provide an improved substrate holder.
In one aspect, an apparatus for processing a substrate is provided. The apparatus comprises a substrate holder having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has one or more support elements configured to support a substrate of a particular size in a support plane defined by the one or more support elements. The substrate holder has an annular groove configured to surround an outer edge of the substrate when the substrate is supported on the one or more support elements. The groove has a depth of at least 25% of the thickness of the substrate holder.
In another aspect, an apparatus for processing a substrate is provided, comprising a reaction chamber, a plurality of heating elements configured to heat the reaction chamber, and a substrate holder in the reaction chamber. The substrate holder has a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has one or more support elements configured to support a substrate of a particular size within a support plane defined by the one or more support elements. The substrate holder has an annular groove configured to surround an outer edge of the substrate when the substrate is supported on the one or more support elements. The groove has a depth of at least 25% of the thickness of the substrate holder.
In another aspect, an apparatus for processing a substrate is provided. The apparatus comprises a substrate holder having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has a support surface sized to support a substrate of a particular size in a support plane. The substrate holder has an annular groove sized to surround an outer edge of the substrate when the substrate is supported on the support surface. The groove has a depth of at least 25% of the thickness of the substrate holder.
In another aspect, an apparatus for processing a substrate is provided. The apparatus comprises a substrate holder having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has a support surface sized to extend underneath and support a substrate of a particular size in a support plane. The substrate holder has a plurality of annular grooves that surround the support surface. Each of the grooves has a depth of at least 25% of the thickness of the substrate holder.
In another aspect, an apparatus for processing a substrate is provided. The apparatus comprises a substrate holder having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has a support surface sized to support a substrate of a particular size in a support plane. The substrate holder has an annular groove sized to surround an outer edge of the substrate when the substrate is supported on the support surface. The groove has a depth of at least 1.5 mm.
In another aspect, a method of manufacturing an apparatus for processing a substrate is provided. A substrate holder is formed having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has one or more support elements configured to support a substrate of a particular size in a support plane defined by the one or more support elements. A first annular groove is formed in the substrate holder. The groove is configured to surround an outer edge of the substrate when the substrate is supported on the one or more support elements. The groove has a depth of at least 25% of the thickness of the substrate holder.
In yet another aspect, a method of manufacturing an apparatus for processing a substrate is provided. According to the method, a substrate holder is formed having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has a support surface configured to extend under and support a substrate of a particular size in a support plane defined by the substrate holder. One or more annular grooves are formed in the substrate holder, each of which surrounds the support surface. The grooves each have a depth of at least 25% of the thickness of the substrate holder.
In yet another aspect, a method of manufacturing an apparatus for processing a substrate is provided. According to the method, a substrate holder is formed having a thickness defined as a distance between generally parallel top and bottom surfaces of the substrate holder. The substrate holder has one or more support elements configured to support a substrate of a particular size in a support plane defined by the one or more support elements. A first annular groove is formed in the substrate holder. The groove is configured to surround an outer edge of the substrate when the substrate is supported on the one or more support elements. The groove has a depth of at least 1.5 mm.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.